' global conservation of energy can't even be defined for
the universe '
Brent

It means that global conservation of energy is infinite .

No, it means it's undefined - there's no unique way to add up the energy from different
parts of a curved spacetime without an timelike Killing field - which describes our universe.

Brent

And this infinite energy belong to the vacuum because that
more than 90% of mass ( dark mass/energy ) is hidden in the vacuum
How to understand vacuum's infinity ?
Vacuum's infinity has only one physical parameter: T=0K.